The liberal blowback is coming fast against the four Democratic senators who voted against expanding background checks for gun buyers today in the Senate. Every Republican senator — save for Sen. Mark Kirk of Illinois, Susan Collins of Maine, Pat Toomey of Pennsylvania and John McCain of Arizona — was expected to oppose it and did. But the Dems — largely from gun-friendly states — are leaving some of their major supporters who don’t live in such climes shaking their heads.

Calling it a “pretty shameful day” in Washington President Obama said: “The American people are trying to figure out how can something that has 90 percent support not happen?”

Liberals are trying to figure out how four Dems –Sens Max Baucus, of Montana, Heidi Heitkamp, of North Dakota, Mark Begich of Alaska, and Mark Pryor from Arkansas — didn’t vote for it. (Senate Majority Leader Harry Reid, D-Nev. also voted against it — but that was a procedural move so he could call up the vote again.)

It’s Heitkamp, who is not facing re-election until 2018, who is getting a lot of heat on this. We’re wondering how Sen. Dianne Feinstein is feeling towards Heitkamp.

Remember when we told you when DiFi threw a $35,800-a-couple fundraiser for Heitkamp last year in San Francisco? If payback’s a pain, then NO payback is REALLY painful.

In a note just blasted out, the Couragers asked folks to sign a petition that said:

“I won’t donate a dime or lift a finger for any Democrat who opposes universal background checks — or any party committee like the DSCC or DNC that spends money to get them elected.”

“We have just as much financial muscle as the NRA and the public on our side.

“Tell the DNC and DSCC you won’t donate a single penny to any Senator who opposes universal background checks for gun purchases. We’re the activists, the Democratic base. We’re the people who donate in elections, knock on doors, and get out the vote in tight elections. We’re the difference on Election Day all around the country.”

Organizing for America — which grew out of President Obama’s re-election effort — is holding events on Saturday in states represented by wobbly senators.

East Bay Rep. Eric Swalwell — a former Alameda County prosecutor — blasted the Senate’s “cowardice on gun safety.”

Here’s Heitkamp’s statement explaining why she voted this way:

“I’ve been adamant from the very beginning of this conversation that the focus should be on mental health issues, full and accurate reporting into the NICS database and ensuring that we are prosecuting criminals in possession of or trying to possess firearms. This conversation should be about what is in people’s minds, not about what is in their hands. I commend Senators Manchin and Toomey for working so hard to bring a serious bill to the floor. However, in its current form I do not see a path for my support. I’ve thought long and hard about this, I’ve taken the tough meetings, and I’ve heard overwhelmingly from the people of North Dakota; and at the end of the day my duty is to listen to and represent the people of North Dakota.”